并查集

package structures;

public class UnionFind1 implements UF {

    private int[] id;

    public UnionFind1(int size) {
        id = new int[size];
        for (int i = 0; i < id.length; i++) {
            id[i] = i;
        }
    }

    @Override
    public int getSize() {
        return id.length;
    }

    private int find(int p) {
        if (p < 0 || p >= id.length) {
            throw new IllegalArgumentException("index is illegal");
        }

        return id[p];
    }

    @Override
    public boolean isConnected(int p, int q) {
        return find(p) == find(q);
    }

    @Override
    public void unionElements(int p, int q) {
        if (find(p) == find(q)) {
            return;
        }

        int pId = find(p);
        int qId = find(q);

        for (int i = 0; i < id.length; i++) {
            if (id[i] == pId) {
                id[i] = qId;
            }
        }
    }
}

package structures;

public class UnionFind2 implements UF {

    private int[] parent;

    public UnionFind2(int size) {
        parent = new int[size];
        for (int i = 0; i < parent.length; i++) {
            parent[i] = i;
        }
    }

    @Override
    public int getSize() {
        return parent.length;
    }

    private int find(int p) {
        if (p < 0 || p >= parent.length) {
            throw new IllegalArgumentException("index is illegal");
        }

        while (parent[p] != p) {
            p = parent[p];
        }

        return p;
    }

    @Override
    public boolean isConnected(int p, int q) {
        return find(p) == find(q);
    }

    @Override
    public void unionElements(int p, int q) {

        int pRoot = find(p);
        int qRoot = find(q);

        if (pRoot == qRoot) {
            return;
        }

        parent[pRoot] = qRoot;

    }
}

package structures;

public class UnionFind3 implements UF {

    private int[] parent;
    private int[] sz;

    public UnionFind3(int size) {
        parent = new int[size];
        sz = new int[size];
        for (int i = 0; i < parent.length; i++) {
            parent[i] = i;
        }

        for (int i = 0; i < sz.length; i++) {
            sz[i] = 1;
        }
    }

    @Override
    public int getSize() {
        return parent.length;
    }

    private int find(int p) {
        if (p < 0 || p >= parent.length) {
            throw new IllegalArgumentException("index is illegal");
        }

        while (parent[p] != p) {
            p = parent[p];
        }

        return p;
    }

    @Override
    public boolean isConnected(int p, int q) {
        return find(p) == find(q);
    }

    @Override
    public void unionElements(int p, int q) {

        int pRoot = find(p);
        int qRoot = find(q);

        if (pRoot == qRoot) {
            return;
        }

        if (sz[pRoot] < sz[qRoot]) {
            parent[pRoot] = qRoot;
            sz[qRoot] += sz[pRoot];
        } else {
            parent[qRoot] = pRoot;
            sz[pRoot] += sz[qRoot];
        }


    }
}

package structures;

public class UnionFind4 implements UF {

    private int[] parent;
    private int[] rank;

    public UnionFind4(int size) {
        parent = new int[size];
        rank = new int[size];
        for (int i = 0; i < parent.length; i++) {
            parent[i] = i;
        }

        for (int i = 0; i < rank.length; i++) {
            rank[i] = 1;
        }
    }

    @Override
    public int getSize() {
        return parent.length;
    }

    private int find(int p) {
        if (p < 0 || p >= parent.length) {
            throw new IllegalArgumentException("index is illegal");
        }

        while (parent[p] != p) {
            p = parent[p];
        }

        return p;
    }

    @Override
    public boolean isConnected(int p, int q) {
        return find(p) == find(q);
    }

    @Override
    public void unionElements(int p, int q) {

        int pRoot = find(p);
        int qRoot = find(q);

        if (pRoot == qRoot) {
            return;
        }

        if (rank[pRoot] < rank[qRoot]) {
            parent[pRoot] = qRoot;
        } else if (rank[pRoot] > rank[qRoot]){
            parent[qRoot] = pRoot;
        } else {
            parent[qRoot] = pRoot;
            rank[pRoot] += 1;
        }


    }
}

package structures;

public class UnionFind5 implements UF {

    private int[] parent;
    private int[] rank;

    public UnionFind5(int size) {
        parent = new int[size];
        rank = new int[size];
        for (int i = 0; i < parent.length; i++) {
            parent[i] = i;
        }

        for (int i = 0; i < rank.length; i++) {
            rank[i] = 1;
        }
    }

    @Override
    public int getSize() {
        return parent.length;
    }

    private int find(int p) {
        if (p < 0 || p >= parent.length) {
            throw new IllegalArgumentException("index is illegal");
        }

        while (parent[p] != p) {
            parent[p] = parent[parent[p]];
            p = parent[p];
        }

        return p;
    }

    @Override
    public boolean isConnected(int p, int q) {
        return find(p) == find(q);
    }

    @Override
    public void unionElements(int p, int q) {

        int pRoot = find(p);
        int qRoot = find(q);

        if (pRoot == qRoot) {
            return;
        }

        if (rank[pRoot] < rank[qRoot]) {
            parent[pRoot] = qRoot;
        } else if (rank[pRoot] > rank[qRoot]){
            parent[qRoot] = pRoot;
        } else {
            parent[qRoot] = pRoot;
            rank[pRoot] += 1;
        }


    }
}

package structures;

public class UnionFind6 implements UF {

    private int[] parent;
    private int[] rank;

    public UnionFind6(int size) {
        parent = new int[size];
        rank = new int[size];
        for (int i = 0; i < parent.length; i++) {
            parent[i] = i;
        }

        for (int i = 0; i < rank.length; i++) {
            rank[i] = 1;
        }
    }

    @Override
    public int getSize() {
        return parent.length;
    }

    private int find(int p) {
        if (p < 0 || p >= parent.length) {
            throw new IllegalArgumentException("index is illegal");
        }

        if (p != parent[p]) {
            parent[p] = find(parent[p]);
        }

        return parent[p];
    }

    @Override
    public boolean isConnected(int p, int q) {
        return find(p) == find(q);
    }

    @Override
    public void unionElements(int p, int q) {

        int pRoot = find(p);
        int qRoot = find(q);

        if (pRoot == qRoot) {
            return;
        }

        if (rank[pRoot] < rank[qRoot]) {
            parent[pRoot] = qRoot;
        } else if (rank[pRoot] > rank[qRoot]){
            parent[qRoot] = pRoot;
        } else {
            parent[qRoot] = pRoot;
            rank[pRoot] += 1;
        }


    }
}